In known types of machines, the units for preparation and delivery of the beverage generally comprise a collecting device with a seat for receiving the disposable cartridge. Once the cartridge has been inserted in the collecting device seat, pressurised water is introduced into the cartridge, via an inlet port, to form a beverage consisting of a solution or a dispersion in water of the soluble product which is delivered via an outlet port on the cartridge.
As the disposable cartridges are originally sealed to prevent outflow of the soluble product during handling, the collecting device is generally provided with a piercing member which opens one or more outlet ports on a wall of the cartridge, for example on the bottom of it, along a number of pre-formed breaking lines.
In known types of machines, the particular shape of the cartridge promotes the formation of a turbulent flow inside the cartridge, thus permitting mixing of the soluble product in the water. The beverage thus formed is released via the outlet ports defined by the above-mentioned breaking lines and/or by outlet ports in the piercing member.
A unit for the preparation of beverages of this type has a number of disadvantages. It has been observed that the turbulence mixing which takes place in the cartridge is not equally efficient and complete for different granulometries of soluble products, for example soluble products for coffee, cappuccino, tea and the like.
In fact, the outlet ports that form on the bottom of the cartridge due to the piercing are too large and can cause the delivery of non-dissolved product and clots of it from the cartridge, for example at the beginning of delivery.
The outflow of particles of non-dissolved soluble product not only lowers the quality of the beverage produced but can cause partial or total obstruction of the beverage outlet ports due to deposit of said particles on the walls of the outlet ports or channels downstream of the outlet ports with respect to the dispersion flow.